A computing device (e.g., mobile phone) may automatically time out when the device does not detect user activity (e.g., does not receive a user input via a keypad or touch screen) for a time-out period. The time-out period may restart each time user activity is detected. When the device times out, the device may turn off the display to conserve battery life and/or enter a lock mode. When the device is in the lock mode, the user may unlock the device (e.g., by entering a password or tracing a pattern on a touch screen).